Plate stretcher



' Oef. 31, 1967` K. POLLAK PLATE STRETCHER 4 sheets-sheet 1l Filed May 24, 1965 Y E .QQ

INVENTOR. K10/W' POLLA/f ATTR/VEKS.

Oct. 31, 1967 K.PO1 LA`K vPLATE STRETCHER 4 Sheets-Sheet 2 l FiledMay 24, 1965 mi WQ INVENTOR.

v /rwar POLLA/r K. POLLAK PLATE s'TRETcHER Oct. 3l, 1967 Filed May 24, 1965 4 Sheets-Sheet 5 1 NVEN TOR. KURT POLL A l( ATTRNEVS.

gripper head and United States Patent Utilice 3,349,598 PLATE STRETCHER Kurt Pollak, Havertown, Pa., assigner to Baldwin-Lima- Hamilton Corp., Philadelphia, Pa. Filed May 24, 1965, Ser. No. 458,234 13 Claims. (Cl. 72-295) This invention relates to a plate stretcher. In particular, this invention relates to a plate stretcher having blocking means to prevent rearward high energy flyback of the gripper jaws.

Metal plate stretchers have heretofore been used for the purpose of obtaining smooth stress-relieved, flat plates from roll or temperature distorted plates by stretching the metal slightly beyond its yield point. The plate stretchers usually comprise gripper heads which tightly grip the ends of the plate while a force is applied to one the other is held stationary. During the stretching operation, it is not unusual for the plate to tear, due to weak spots or rolling faults. When the plate fails, the pulling force is suddenly released and great amounts of potential energy stored in the plate and stretcher components are released. The potential energy is derived from the resiliency of the plate stretcher components as well as the compressibility of the hydraulic uid in the stretch force producing cylinder.

In one of the more common types of plate stretcher, the tightness of the gripper jaws is obtained by a wedging action which increases the tightness of the jaws as the pulling force of the machine increases. When a plate fails, the stored potential energy is suddenly converted into kinetic energy and a shock-like movement of the gripper jaws occurs. This sudden release of the potential energy releases the gripper jaw hold on the plate and forces the jaws together with the plate remnant with great impact force toward the throat of the gripper head. The size of this force is so great that the machine can be severly damaged by it. In order to prevent such damage, and at the same time prevent clogging of the jaw teeth with sheared oil metal, this invention provides a means to block the rearward movement of remnants.

It therefore is the general object of the present invention to provide a new and improved plate stretcher.

It is another object of the present invention to provide a novel plate stretcher having gripper jaw blocking means.

It is still another object of the present invention to provide a novel plate stretcher having individual wedges for blocking the gripper jaws.

It is yet another object of the present invention to provide a plate stretcher having novel gripper jaws for blocking rearward movement of a plate remnant.

It is yet another object of the present invention to provide a novel plate stretcher having a plurality of vertically disposed blocking wedges behind selected individual gripper jaws.

It is still another object of the present invention to provide a novel plate stretcher having means to eliminate the possibility of damage to the gripper head assemblies.

It is a further object of the present invention to provide a novel gripper head assembly for preventing clogging of jaw insert teeth.

Other objects will appear hereinafter.

For the purposes of illustrating the invention, there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1A is a longitudinal sectional view of a por tion of the plate stretcher including the movable gripper head assembly.

FIGURE 1B is a side view of a second portion of the the jaws and plate e 3,349,598 Patented Oct. 31, 1967` plate stretcher illustrating the stationary gripper head aS- sembly.

FIGURES lA and 1B are plate stretcher when to the right.

FIGURE 2 is a top plan view of the plate stretcher shown in FIGURES 1A and 1B taken along the line 2-2.

FIGURE 3 is a sectional View of one of the gripper head assemblies shown in FIGURES lA and 1B.

FIGURE 4 is a partial sectional view of the gripper head assembly illustrated in FIGURE 3 taken along the line 4 4.

FIGURE 5 is a partial sectional view of the gripper head assembly illustrated in FIGURE 3 taken along the line 5-5.

Referring now in detail to the drawings, wherein like numerals indicate like elements, there is shown in FIGURES 1A and 1B a plate stretcher designated generally as 10.

As shown, the plate stretcher 10 comprises a base 12 which is supported in a foundation 13. The plate stretcher includes a movable gripper head assembly 14 and a stationary gripper head assembly 16 mounted on rails 22 and 24. The rails 22 and 24, which are supported by the base I2, extend longitudinally of the vplate stretcher 12.

The stationary gripper head assembly 16 is adapted to be slid along the rails 22 and 24 and xed in a predetermined position. The stationary gripper head 16 is provided with guide slots (not shown) that cooperate with the rail 22 and 24. .To fix the position Iof the gripper head assembly 16, the rails 22 and 24 are provided with a plurality of elongated holes 26 having their major axis parallel to the plate stretcher longitudinal axis. Tabs such as the tab 28 depend from either side of the gripper head assembly 16 and have holes extending therethrough in a position adapted to be aligned with the holes 26. Depending on the size of plate to be stretched, the stationary gripper head assembly 16 is moved to a position wherein the holes in tabs 28 are aligned with elongated holes 26. Thereafter, a locking pin 30 is passed through the tab holes and holes 26 to fix the position of gripper head assembly 16.

The plate stretcher 10 is provided with a back up block 32 which is supported on the rails 22 and 24 by four rollers 34, 36, 38 and 40, mounted on axles 42, 44, 46 and 48 laterally extending from back up block 32. The back up block 32 is fixed in position by means of a locating pin 50 that extends through one of the holes 26 and the block 32.

A pair of hydraulic shock absorbers 52 and 54 extend between the stationary gripper head assembly 16 and the back up block 32. The shock absorbers 52 and 54 are adapter to take up the shock due to the displacement of gripper head assembly 16 Within the elongated hole 26. That portion of the shock which is not absorbed by shock absorbers 52 and 54 is transmitted to the rails 22 and 24. A pair of hydraulic shock absorbers 56 and 58 extend between the plate stretcher 10 and foundation 13.

The movable gripper head assembly 14 is slidably mounted on rails 22 and 24 in a conventional manner. The gripper head assembly 14 is moved in the stretch direction by a stretch -cylinder ram 60. The ram 60 comprises a cylinder 62 adapted to receive the piston 64. The piston 64 is held in lluid tight telescoping relation with the cylinder 62 by means of a cylindrical ange 66 -bolted to the cylinder 62. By adjusting the llange bolt 68, the ring seal 70 is brought into proper contact against piston 64 to provide the necessary duid tight sealing engagement between the cylinder 62 and piston 64. The ring seal 70 is held in position by means of bushing 72 used for guidadapted to form a single placed end to end with FIGURE 1B ing piston 64. The piston 64 is caused to reciprocate within cylinder 62 by feeding hydraulic fluid through the inlet 74 which is connected to appropriate hydraulic fluid pumping means through conduit 76.

The cylinder 62 is fixedly supported within the cylinder mounts 78 and 80 which extend upwardly from the cylinder crosshead 82. A crosshead 84 is xed to the piston 64 adjacent the rearmost end thereof. T-he crosshead 84 is slidably supported on the crosshead support 86. Four connecting rods extend from crosshead 84 through mounts 78 and 80 to the movable gripper head assembly 14. Three of the four connecting rods 88, 90 and 92 are shown in FIGURES 1A and 2. The fourth connecting rod is hidden from View in FIGURE 2 by rod 92. As shown, the connecting rods are fixed to the crosshead 84 and moving gripper head assembly 14 so that the displacement of piston 64 causes equal displacement of the gripper head assembly 14.

A pair of hydraulic cylinders 102 and 104 are used to advance and retract the gripper head. These cylinders also serve as hydraulic shock absorbers of shock forces transmitted through the gripper head.

The cylinders are resilient-mounted to the gripper head through attachments 94 and 96. Stop plates 98 and 100 stop the gripper head in the fully open position.

In operation, the gripper head assemblies 14 and 16 are adjusted to a position for receiving the plate 106 to be stretched. Once adjusted, the plate 106 is held tightly within the gripper head assemblies by means to be described below. Then hydraulic fluid is fed into the cylinders 102, 104 and 62 thereby moving the movable gripper head assembly 14 rearwardly and stretching the plate 106 with the required force.

Since the stationary and movable gripper head assemblies are similar in constr-uction, with the exceptions described above, only the movable gripper head assembly 14 will be described in detail. Where appropriate, elements of the stationary gripper head assembly 16 that are the same as those shown in the movable gripper head assembly 14 will be designated with primed numerals.

Referring now to FIGURES 3 to 5, the movable gripper head assembly 14 is shown in position gripping the edge of plate 106. The opening 108 is elongated and extends transversely across the front face of gripper head assembly 14. The wedge-shaped opening 108 is in open communication with a chamber 109 that is immediately behind opening 108.

As best shown in FIGURES 3 and 4, the opposed faces 111 and 113 of the throat opening 108 support a plurality of paired jaw block supports 110 and 112. The jaw block supports 110 and 112 are mounted to faces 111 and 113 so that their adjacent faces incline away from each other in a direction from front to rear of the gripper head assembly 14. Jaw block supports 110 and 112 are formed so that the angle of inclination of their adjacent faces has an apex forward of the assemblies 14 at the central plane of plate 106.

A pair of jaw blocks 18 and 20 are mounted in sliding engagement with each of the jaw block supports 110` and 112. The jaw blocks 18 and 20 may also be referred to as gripper jaws. Each of the jaw blocks 18 and 20 is shaped so that when slidingly engaged with the jaw block supports 110 and 112, their adjacent surfaces 114 and 116 are in opposed parallel relationship. Proper sliding engagement is assured by providing dovetail tenons 122 and 124 4depending from the jaw block surfaces 118 and 120 and providing mating dovetail mortise grooves 126 and 128 in the jaw block supports 110 and 112.

The blocks 18 and 20 are initially moved into and out of engagement with the plate 106 yby means of a jaw block adjustment assembly designated generally as 130. The jaw block adjustment assembly includes a support 132 fixed to the rear face of gripper head 14. Support 132 supports the bridge 134 which is held in spaced-away relation from the rear face of gripper head 14 by spacers 136 and 138. A jaw block cylinder 140 is mounted to the rear of bridge 134 and has a piston 142 reciprocally mounted therein.

A rod 134 extends through an opening in cylinder 140 to threadedly engage the yoke 146. By properly feeding hydraulic fluid (through the conduits 148 and 150) into the cylinder to selected sides of piston 142, the yoke 146 can be selectively reciprocated. The yoke 146 is connected to the jaws 18 and 20 by means of upper and lower connecting rods 152 and 154. As can be seen from FIG- URE 4, there are two upper connecting rods 152 and two low-er connecting rods 154 extending from either side of the yoke 146. These rods are pivotally mounted to the yoke by means of pins 156 and 158. Similarly, the rods 152 and 154 are pivotally connected to jaws 18 and 20 by means of pins 160 and 162.

From the foregoing, it may be seen that the jaws 18 and 20 can be brought into sliding engagement or disengagement with plate 106 by forcing hydraulic uid through either conduit 148 or conduit 150. Appropriate uid pumps (not shown) are provided for this purpose. As the angle of inclination of jaw block surfaces 118 and 120 is equal and parallel to surfaces 111 and 113, the space between jaw block surfaces 114 and 116 uniformly decreases as the jaw blocks 18 and Z0 are moved forward by the jaw block adjustment assembly 130. If desired, the jaw blocks 18 and 20 may be provided with removable jaw block inserts 164 and 166 which have parallel opposed surfaces for engaging the plate 106.

In operating the plate stretcher, the jaw block inserts 164 and 166 are brought into engagement with the plate 106. A stretching force is applied thereto by moving assembly 14. The stretching force tends to pull jaws 18 and 20 forward on the jaw block supports 110 and 112. As the jaw blocks 18 and 20 are pulled forward, they are also forced into tighter engagement with the plate 106 due to the inclination of surfaces 118 and 120, which in effect wedges the blocks together. This type of 4gripper head assembly construction permits the gripper head to retain the plate 106 while extremely high stretching forces are applied to it.

The faces of inserts 164 and 166 are provided with serrations to aid in gripping the work. Preferably, the serrations are of a saw tooth design.

While the plate 106 is under stress, it is not unusual for an undetected fault in its structure to cause the plate to fail and thereby separate into two or more pieces. When this happens, the tremendous stretching forces developed between the gripper head assemblies 14 and 16 are suddenly released and their energy must be absorbed. Most of this energy is absorbed by the hydraulic shock absorbers described above. However, the failure of plate 106 releases the wedge-like gripping action of jaws 18 and 20 and they tend to fly back into the chamber 109. Similarly, the remnant of plate 106 between the jaws 18 and 20 also moves rearwardly toward the chamber 109. The impact force created by jaws 18 and 20 together with the remnant of plate 106 can severely damage both the jaw block adjustment assembly 130 and the gripper head aS- sembly 14.'To prevent this, a wedge mechanism has been provided.

Referring to FIGURES 3 and 5, it will be noted a wedge 168 has been disposed in juxtaposition to the real' surfaces of blocks 18 and 20. As shown, the Wedge 168 includes a rst surface 170 that is parallel to the rear surfaces of blocks 18 and 20 and therefore normal to the plate stretcher axis. The wedge-shape of wedge 168 is defined by the second inclined surface 172 which if extended would intersect surface 170. Surface 172 is provided with a dovetail shaped mortise which receives a similarly shaped tenon 174 extending from a slide block 176. The surface of slide block 1.76 is parallel to wedge surface 17 2 and therefore inclined at the same angle.

A pair of socket head cap screws 178 and 180 fix slide block 176 to gripper head assembly 14. Slide blocks 176 are appropriately countersunk to receive screws 178 and 180.

In the position shown, the wedge 176 blocks any rrearward movement of gripper jaws 18 and 20. The rearward force developed when a plate 106 fails is transferred through the wedge 168 to the slide block 175 and into the gripper head assembly where it is absorbed by the means described above.

Each set of gripper jaws 18 and 20 is provided with a wedge with hydraulic cylinder and piston to slide the wedge into blocking position. As shown in FIGURE 3, the wedge is mounted to be moved in a direction having a vertical and horizontal component. The means for so moving the wedges 168 is provided by hydraulic cylinder 182 and a reciprocal piston 184 mounted therein. The piS- ton is connected to wedges 168 through extension rods 186. Rods 186 are mounted so as to be parallel to wedge surface 172 and the corresponding surface of slide block 176. Piston 184 and hence extension rods 186 are reciprocated by selectively applying hydraulic fluid pressure through conduits 188 and 190.

By mounting rod 186 so it is parallel to surface 172, the wedge 168 has two components of movement. Thus, it has a perpendicular or vertical component of movement and a horizontal component of movement. Since surface 170 is parallel to the back surfaces of jaws 18 and 20, Le., the horizontal component, the wedging force of wedge 168 will act uniformly on both of the jaw blocks 18 and 20. This assures Vthat both jaw blocks are backed-up uniformly. If the surface of Wedge 168 were at an angle rather than being vertical, jaw block 18 might be forced to move first and thereby push the plate 166 out of its proper position on the jaw block 20. Moreover, this arrangement eliminates the necessity of machining the back surfaces of the jaws at odd angles, which would be expens1ve.

To prevent the remnant of plate 106 from flying back into the cavity 109, the jaw block 20 is provided with a stop 192 that extends towards the surface 114 of jaw block 18. The stop 192 provides a shoulder which acts as a back stop for preventing rearward movement of any remnant of plate 106. This also eliminates clogging of the jaw inserts.

In operation, the plate 106 is mounted within the jaw blocks 18 and 20 so that its edge is in abutting Contact with flange 192. Thus, the purpose in designing wedge 168 so that jaw blocks 18 and 20 move together and do not force plate -6 away from flange 192 becomes all the more apparent.

As has been described and shown, the plate stretcher includes four sets of jaw blocks 18 and 20 with four individually operable wedges to block each set of jaw blocks in the forward plate gripping position. However, it will be readily recognized by those skilled in the art that any number of jaw blocks may be provided depending upon the size and design of the machine. Furthermore, the machine may be designed such that only selected sets of jaw blocks 18 and 20 have wedges behind them. Thus, if the machine were to have ten sets of jaw blocks, it may be necessary to provide wedges only for the center 6. Thus, the damaging effects described above are not as prevalent in regard to the outer jaw blocks.

The present invention may be embodied in other specic forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

I claim:

1. In a plate stretcher including a stationary gripper head assembly and a movable gripper head assembly, each gripper head assembly having a pair of angularly disposed spaced apart faces, a plurality of paired gripper jaws slidingly supported in opposed relation on said faces, said faces being at an angle such that the forward edges thereof are closer than the rear edges, whereby said jaws move closer together as they slide toward forward edge of said faces, a wedge behind selected sets of jaws, and

means to move said wedges to a position blocking rearward movement of the gripper jaws.

2. In a plate stretcher including a stationary gripperl head assembly and a movable gripper head assembly, each gripper head assembly having a pair of opposed faces inclined toward each other with the apex of the angle of inclination being adjacent the front of the gripper head assembly, a plurality of sets of gripper jaws slidingly supported in spaced apart opposed relation on said faces, whereby said gripper jaws in each set move toward each other when slid forward on said faces, individual wedge means rearward of selected sets of gripper jaws, and means to move each said wedge into blocking position between said gripper jaws and said gripper head asesmbly.

3. A plate stretcher in accordance with claim 2 wherein means are provided for sliding said gripper jaws, said means including an expandable chamber motor, and connecting rods for connecting said motor to said gripper jaws.

4. A plate stretcher in accordance with claim 2 wherein one of said gripper jaws in each set includes a stop shoulder projecting towards the other gripper jaw.

5. In a plate stretcher including a first gripper head assembly and a second gripper head assembly, each gripper head assembly having opposed faces inclined toward each other with the apex of the angle of inclination being adjacent the front of the gripper head assembly, a plurality of paired sets of gripper jaws slidingly supported in opposed relation on said faces, each said gripper jaw having a gripping surface, an inclined surface and a back surface, said inclined surface being at the same angle as said faces and slidingly associated with said faces, blocking means movable to a position intermediate the back surface of selected gripper jaws and a portion of the gripper head assembly for blocking rearward movement of said gripper jaws.

6. A plate stretcher in accordance with claim 5 wherein said portion of the gripper head assembly is a slide block fixed to said assembly.

7. In a plate stretcher including a stationary gripper head assembly and a movable gripper head assembly, each gripper head assembly having opposed faces inclined towards each other with the apex of the angle of inclination being adjacent the front of the gripper head assembly, said faces extending transversely of the plate stretcher axis, a plurality of paired sets of gripper jaws slidingly supported in opposed relation on said faces, each gripper jaw including a Igripping surface, an inclined surface and a back surface, sai-d inclined surfaces being at the same angle as the face on which the jaw is supported, means for reciprocating said jaws on said faces, the back surfaces of said blocks being normal to the plate stretcher axis, and wedge means movable to a position intermediate the back surface of selected sets of gripper jaws and a portion of said gripper head assembly, each wedge having a surface parallel to said back surfaces and a surface inclined away from said parallel surfaces, said parallel surface and inclined surface defining the apex of said Wedge, and means to move said wedge into said intermediate position for wedging said jaws in gripping relation.

8. A plate stretcher in accordance with claim 7 wherein said wed-ge moving means comprises an expandable chamber motor and a rod connecting said motor to said wedges, said connecting rod being parallel to the inclined surfaces of said wedges.

9. A plate stretcher in accordance with claim 7 wherein said means for sliding said gripper jaws includes an expandable chamber motor and connecting rods for connecting said motor to said gripper jaws.

10. A plate stretcher in accordance with claim 7 wherein one of the gripper jaws in each set includes a stop shoulder projecting outwardly from the gripping surface towards the other gripper jaw, said shoulder being spaced away from the forward edge of the gripper jaws.

11. A plate stretcher in accordance with claim 7 wherein said portion of the Igripper head assembly includes a slide block fixed to said assembly at a position spaced rearwardly from said back surfaces, said block including a wedge -contacting surface parallel to the inclined wedge surface.

12. A plate stretcher comprising a stationary gripper head `assembly in spaced apart facing relation to a displaceable gripper head assembly, a displaceable gripper head assembly, means to adjustably lock said stationary gripper head assembly a predetermined distance from the initial position of said displaceable gripper head assembly, means to displace said displaceable gripper head assembly away from said initial position, said displacement means including a hydraulic stretch cylinder ram and connecting rods, each gripper head assembly having spaced apart opposed planar surfaces inclined toward each other with the apex of the angle of inclination being intermediate said gripper head assemblies, a plurality of paired sets of gripper jaws in sliding engagement with said planar surfaces, each gripper jaw having a gripping surface, an inclined surface and a back surface, said inclined surface being parallel to and in abutting relation with a planar surface, means to slide said paired jaws forwardly and rearwardly on said surfaces, the back surfaces of said jaws being normal to the plate stretcher axis, wedge means positionable intermediate the back surface of selected sets of gripper jaws and a slide block fixed to said gripper head assembly, each wedge having a surface parallel to said back surfaces, each wedge having a surface inclined away from said parallel surfaces, said parallel surface and inclined surface defining the angled surfaces of said wedges, and means to move said wedges into position with said inclined surface abutting said slide block and said parallel surface abutting said back surfaces for blocking rearward movement of said jaws, said moving means including a plurality of pistons reciprocally mounted within cylinders, and rods connecting said pistons to said wedges, said rods being parallel to said inclined wedge surfaces.

13. In a plate stretcher including a pair of gripper head assemblies, each gripper head assembly including a pair of angularly disposed spaced apart faces, a plurality of paired lgripper jaws slidingly supported in opposed relation on said faces, said faces being at an angle such that the forward edges thereof are closer together than the rear edges, whereby said jaw is moved closer together as they slide toward the forward edge on said faces, blocking means behind selected sets of jaws, and means to move said blocking means to a position blocking rearward movement of the gripper jaws.

References Cited UNITED STATES PATENTS 5/1956 Wheeler et al. 72-296 8/1962 Hill et al 72-302 

1. IN A PLATE STRETCHER INCLUDING A STATIONARY GRIPPER HEAD ASSEMBLY AND A MOVABLE GRIPPER HEAD ASSEMBLY, EACH GRIPPER HEAD ASSEMBLY HAVING A PAIR OF ANGULARLY DISPOSED SPACED APART FACES, A PLURALITY OF PAIRED GRIPPER JAWS SLIDINGLY SUPPORTED IN OPPOSED RELATION ON SAID FACES, SAID FACES BEING AT AN ANGLE SUCH THAT THE FORWARD EDGES THEREOF ARE CLOSER THAN THE REAR EDGES, WHEREBY FORWARD EDGE MOVE CLOSER TOGETHER AS THEY SLIDE TOWARD FORWARD EDGE OF SAID FACES, A WEDGE BEHIND SELECTED SETS OF JAWS, AND MEANS TO MOVE SAID WEDGES TO A POSITION BLOCKING REARWARD MOVEMENT OF THE GRIPPER JAWS. 